E1_2 - 1 OBJECTIVE I. To study the basic functions and...

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OBJECTIVE I. To study the basic functions and controls of a typical dual trace oscilloscope, Voltage versus voltage measurement Voltage versus time measurement Duty cycle measurement Sine wave measurement II. To familiarize with the operation and use of the function generator. III. To study waveform in a RC circuit INTRODUCTION A cathode-ray oscilloscope (CRT) is essentially an electrostatic instrument. It is extremely versatile equipment, used to display variations of physical qualities in time. The CRT shows electrical oscillations as lines on a glass surface (screen). It works on the principle of displaying a luminescent “spot” on a zinc-sulphate coated screen that is caused by impinging electron beam. For an applied voltage, the beam is deflected proportionally. The CRT is also the only type of indicator that can provide continuous information for fast changing electrical parameters. It can also function as a voltmeter measuring peak voltage for A.C. source and e.m.f for D.C. source. Also overloading will not damage the CRT easily The cathode ray oscilloscope is essential equipment which is used to measure the magnitude of rapidly changing in electric currents, electric potentials, or electric pulses as function of time. The main component of an oscilloscope is the cathode ray tube (CRT). This tube is commonly used to obtain a visual display of electronics information for other applications, including radar systems, television receivers and computers. The CRT is a vacuum tube in which electrons are accelerated and deflected under the influence of electric fields The cathode ray tube contains three main components: the electron gun, the deflection system and the fluorescent screen. Figure 1 Main features of the cathode ray tube (1) (2) (3) Electron gun Deflection system Fluorescent screen Electron Heater Beam Control grid Y-plates Cathode Anodes X-plates Vacuum 1
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(1) The electron gun is an assembly that produced electron beam. It is located in the neck of the tube. It consists of a heater, a cathode, and a positively charged anode. An electric current maintained in the heater causes its temperature to rise, which in turn heats the cathode. The cathode reaches temperatures high enough to cause electron gun to be “boiled off”. The electron gun has a control grid to control the number of electrons reaching the anode. The anode has a hole in its center that allows the electrons to pass through without striking the anode. These electrons, if left undisturbed, travel in a straight-line path until they strike the fluorescent screen. (2) The deflection system is two sets of plates placed at right angles to each other in the neck of the tube. The electron beam is deflected either vertically or horizontally or both. The horizontal pair called the Y-plates and the vertical pair called the X-plates. External electric circuits are used to control and change the amount of charge present on these plates. An increasing charge creates an increasing electric field between the plates, which causes the
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This note was uploaded on 10/18/2009 for the course ECONS 111 taught by Professor Yo during the Spring '09 term at Nassau CC.

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E1_2 - 1 OBJECTIVE I. To study the basic functions and...

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